Control and alarm system for sump pump

ABSTRACT

A control system for a sump pump driven by an AC motor includes an AC power line having an input adapted for connection to an AC power source and an output adapted for connection to the AC drive motor. A controller is connected to a controllable switch in the AC power line, to control the opening and closing of that switch. Redundant float switches are coupled to the controller and adapted to be mounted in a sump to supply the controller with a signals when the liquid in the sump rises to a selected level. A timer in, or coupled to, the controller alters the control signal to open the controllable switch if the liquid level in the sump remains above the selected level for a preselected time period.

FIELD OF THE INVENTION

The present invention relates to control and alarm systems for sumppumps driven by electric motors.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a controlsystem for a sump pump driven by an AC motor comprises an AC power linehaving an input adapted for connection to an AC power source and anoutput adapted for connection to the AC drive motor, a controllableswitch in the AC power line, a controller coupled to the controllableswitch to supply a control signal to the controllable switch to controlthe supply of power to the drive motor, and redundant float switcheseach of which is coupled to the controller and adapted to be mounted ina sump to supply the controller with a signal when the liquid in thesump rises to a selected level.

A timer may be included for producing an alarm signal when the drivemotor has been energized continuously for a preselected time period. Aconnector may be included for supplying the alarm signal to an alarmsystem, which may be an alarm system installed in the building in whichthe sump pump is installed or any security system capable of receivingsuch a signal via a communication link. A backup battery may supplypower to the controller when power is not available from the AC powerline, with a monitor coupled to the battery for producing an alarmsignal when the output voltage of the battery drops below a preselectedlevel. Another monitor may be coupled to the AC power line for producinga battery control signal when power is not available from the AC powerline, with a controllable switch responding to the battery controlsignal for connecting the battery to the controller. A monitor may alsobe coupled to the AC power line for producing an alarm signal when poweris not available from the AC power line or when a brown-out (e.g., linevoltage drops below 90 volts).

An improved dual-float-switch assembly has redundant float switches thatinclude a pair of spaced floats mounted for vertical movement with eachof the floats containing at least one magnetic element, a pair of spacedswitches mounted for actuation by the magnetic elements when the floatsare moved to selected locations relative to the switches, an electricalpower source connected to the switches so that the actuation of theswitches produces electrical output signals indicating the locations ofthe floats relative to the switches, and an apertured containersurrounding the floats to allow vertical movement of the floats in thesump while restricting the access of obstructing particles to the pathof vertical movement of the floats. The apertured container may comprisea generally cylindrical cage surrounding floats that are generallydisc-shaped for movement along the axis of the interior of the cage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of one embodiment of a sump pump control unitembodying the invention;

FIG. 2 is a bottom plan view of the control unit of FIG. 1;

FIG. 3 is a front elevation of the control unit of FIG. 1;

FIG. 4 is a schematic circuit diagram of the electrical circuitry in thecontrol unit of FIG. 1;

FIG. 5 is a front elevation of another embodiment of a sump pump controlunit embodying the invention;

FIG. 6 is a side elevation of the control unit of FIG. 5;

FIGS. 7 a and 7 b taken together form a single schematic circuit diagramof the electrical circuitry in the control unit of FIG. 5;

FIG. 8 is an exploded perspective of a float valve assembly for use withthe control units of FIGS. 1-7;

FIG. 9 is an enlarged end elevation of the left-hand end of the floatvalve assembly as viewed in FIG. 8;

FIG. 10 is an enlarged end elevation of the right-hand end of the floatvalve assembly as viewed in FIG. 8;

FIG. 11 is a longitudinal section of the float valve assembly of FIGS.8-10; and

FIG. 12 is a longitudinal section of the floats and switches in thefloat valve assembly of FIGS. 8-11.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Although the invention will be described in connection with certainpreferred embodiments, it will be understood that the invention is notlimited to those particular embodiments. On the contrary, the inventionis intended to cover all alternatives, modifications, and equivalentarrangements as may be included within the spirit and scope of theinvention as defined by the appended claims.

Two embodiments of the invention will be described. A first embodiment,shown in FIGS. 1-4, is a low-cost embodiment that does not use amicroprocessor. A second embodiment, shown in FIGS. 5-7, is a more fullyfeatured embodiment that uses a microprocessor. A dual-float-switchassembly that can be used in either of the two embodiments is shown inFIGS. 8-12.

The embodiment of FIGS. 1-4 includes a housing 10 that contains controlcircuitry without any indicators or alarms. The power cord of a sumppump having an AC drive motor is plugged into a socket 11 on the frontof the housing 10, and a “piggyback” plug 12 extending outwardly fromthe back of the housing 10 is plugged into a standard power outlet tosupply power to both the control circuitry inside the housing 10 and tothe pump controlled by that circuitry.

A schematic diagram of the control circuitry inside the housing 10 isshown in FIG. 4. The socket 11 and the plug 12 have a common ground line15. Connection of the pump drive motor to the AC power source iscontrolled by opening and closing the contacts 16 a, 16 b of a relay 16having a coil 16 c, the energization of which is controlled by atransistor Q1 that has its emitter and collector connected in serieswith the coil 16 c. Any AC spikes produced by the opening and closing ofthe relay contacts 16 a, 16 b are eliminated, or at least reduced, by asnubber circuit formed by a resistor R1 and a capacitor C1 connectedacross the relay contacts. A diode D1 acts as a ring-back snubber toprevent damage to the transistor Q1 when the pump is turned off.

A timer 17, such as a NE555 IC, is connected via resistor R5 to the baseof the transistor Q1 to turn the transistor Q1 on and off in response toan output signal from either of two float switches 20 and 21 locatedwithin the sump containing the sump pump. The transistor Q1 in turncontrols the energization of the relay coil 16 to turn the drive motoron and off. The float switches 20 and 21 are positioned to be actuatedwhen the liquid level in the sump rises to a selected level at which itis desired to start the sump pump. The two float switches 20 and 21 areconnected in parallel with each other so that they are redundant, whichensures that the timer 17 receives an input signal from the floatswitches even if one of those switches malfunctions. Malfunctioning offloat switches is one of the primary causes of failures of sump pumpsystems.

Both float switches 20 and 21 are connected between a 12-volt DC voltagesupply 18 and ground. A voltage divider formed by a pair of resistors R3and R6 is connected between the 12-volt supply and the float switches,with the mid-point of the voltage divider connected to the triggeringinput TRG of the timer 17 at pin 2. Thus, when one or both of the floatswitches 20 and 21 close, the voltage at the input TRG of the timer 17falls, which causes the timer to produce an output signal at pin 3. Thisoutput signal passes through the resistor R5 to the base of thetransistor Q1, which turns on the transistor, causing current to flowfrom the 12-volt supply though the relay coil 16 and the transistor Q1to ground. Consequently, whenever the transistor Q1 is on, the relaycoil 16 is energized, which closes the relay contacts 16 a, 16 b to turnon the drive motor for the sump pump by supplying power from the plug 12to the socket 11 connected to the power cord of the drive motor.Conversely, when the transistor Q1 is turned off, the relay coil 16 isde-energized, the relay contacts 16 a, 16 b are opened, and the drivemotor is turned off. A diode D4 is connected between the float switchesand the collector of the transistor Q1 to keep the pump motor operatingin the event of a failure of the timer 17.

Both float switches 20 and 21 are also connected to the base of atransistor Q2 which has its collector connected to ground and itsemitter to an RC timing circuit formed by a resistor R4 and a capacitorC5. The transistor Q2 keeps the capacitor C5 discharged while either orboth float switches are closed, i.e., while the sump pump is on. Whenthe liquid level in the sump drops to open the float switches, the timer17 maintains its output signal for 10 seconds to keep the pump on forthis additional time period, and then turns the pump off by turning offthe transistor Q1. A resistor R8 and capacitor C6 connected in seriesbetween the base of transistor Q2 and ground form a noise snubber toremove noise from the float switch lines.

The power input to the timer 17 is the 12-volt supply connected to theVcc input of the timer at pin 8. A filter formed by a resistor R2 andcapacitors C2 and C3 filter noise in the 12-volt supply line to maintainoperation of the timer 17 with filtered voltage.

The 12-volt supply is preferably derived from the AC power sourceconnected to the plug 12. That power source is connected across theprimary winding T1 la of a step-down transformer T1. The secondarywinding T1 b of the transformer T1 is connected to a full-wave rectifierformed by a diode bridge DB to convert the reduced AC voltage from thesecondary winding T1 b to the desired 12 volts DC A capacitor C4smoothes the DC output of the bridge DB.

The more fully featured embodiment of FIGS. 5-7 includes a housing 30that not only contains control circuitry, but also multiple indicatorlights LED1-LED4 (described in detail below) on its front panel 31. Thepower cord of a sump pump having an AC drive motor is plugged into asocket 32 in the front panel 31, and a short power cord 33 extendingfrom the bottom wall of the housing 30 is plugged into a standard poweroutlet to supply power to both the control circuitry inside the housing30 and to the pump controlled by that circuitry, via the pump power cordplugged into the socket 32. The front panel 31 also includes a connector34 for supplying signals (described in detail below) to an alarm system,which may be an alarm system installed in the building in which the sumppump is installed or any security system capable of receiving such asignal via a communication link. in which the sump pump is installed,and an on-off switch SW1 that permits the power-failure alarm (alsodescribed in detail below) to be turned off manually to silence thealarm and to conserve battery power.

A schematic diagram of the control circuitry inside the housing 30 isshown in FIGS. 7 a and 7 b. Elements that are common to the controlcircuitry of FIG. 4 are identified by the same reference numbers in bothfigures, and the description of these common elements will not berepeated. The “float” output signals from the float switches 20 and 21are supplied through a blocking diode D5 to pin 2 of a microprocessor 35(e.g., a Microchip 16C54C powered by an internally derived 5-volt DCsupply, described below. The diode DS blocks the 12 volts that isapplied to the float switches, to protect the microprocessor input. Aresistor R18 connected between the “float” signal line and Vcc is a 5Vpull-up for the “float” input to pin 2 of the microprocessor 35. Acapacitor C6 connected between the diode D5 and ground provides a noisefilter to remove noise on the line connecting the float switches to themicroprocessor 35. A diode D4 is connected between the float switchesand the collector of the transistor Q1 is a pump fail-safe diode thatturns on the pump in the event of a failure of the microprocessor 35.The “float” signal is one of three inputs to the microprocessor 35; theother two are “AC status” and “9V status” signals supplied to pins 17and 18, respectively.

The “AC status” signal is the voltage level at the midpoint of a voltagedivider formed by a pair of resistors R12 and R13 connected between the12-volt supply and ground. This “AC status” voltage is supplied to pin17 of the microprocessor 35 and goes low when power is not availablefrom the AC power line (because the 12-volt supply is derived from theAC power supply) or when a brown-out (e.g., line voltage drops below apreselected voltage such as 90 volts). A resistor R21 is a pull-up forthe “AC status” line to pin 17. A zener diode D7 is connected across theresistor R13 to limit the voltage to a maximum of 5.1V into the pin 17.

The “9V status” signal is produced by a circuit that monitors the outputvoltage of a 9-volt backup battery 40 that can be connected to thecontrol circuitry by a switch SW1. The monitoring circuit includes a FETQ3, such as a 2N7000 which is an N-channel enhancement-mode verticalDMOS FET, whose output (drain) is the “9V status” input to pin 18 of themicroprocessor 35, which goes low to produce an alarm signal when theoutput voltage of the battery drops below a preselected level,indicating that the battery should be replaced or re-charged. A resistorR20 connected between pin 18 and Vcc is a pull-up for the “9V status”input to pin 18. The gate of the FET Q3 is connected to the midpoint ofa voltage divider formed by a pair of resistors R9 and R10 connectedbetween the ground side of the switch SW1 and the collector of atransistor Q4. The emitter of the transistor Q4 is connected to ground,and the base is connected via resistor R11 to the “9VC” output at pin 13of the microprocessor 35, which turns on the battery-voltage-monitoringcircuit. The “9VC” signal from the microprocessor 35 turns on thetransistor Q4 for a very short period of time (just long enough tomeasure the battery voltage and release) every 1 to 5 seconds. Each timethe transistor Q4 is turned on, the FET Q3 supplies the microprocessor35 with an “AC status” signal that is proportional to the current outputvoltage of the battery.

The microprocessor 35 uses the three input signals “float,” “AC status”and “9V status” to produce the following output signals:

-   -   1. a “beep” signal that activates a beeper B whenever an alarm        condition exists, indicating that the user has been notified and        some action may be necessary,    -   2. a “time out” signal that illuminates the light-emitting diode        LED4 whenever the pump motor remains on for a preselected time        period, such as 5, 10 or 15 minutes, indicating that the liquid        level in the sump has remained high for an abnormally long time,    -   3. an “operation” signal that illuminates the light-emitting        diode LED3 to indicate that the controller is functioning and        ready to receive signals from the monitoring system and/or the        float switches.    -   4. a “low battery” signal that illuminates the light-emitting        diode LED2 whenever the 9-volt backup battery voltage is low,        indicating that the battery should be replaced or re-charged,    -   5. an “AC out” signal that illuminates a light-emitting diode        LED1 whenever the AC power is out, indicating that the sump pump        will not be able to operate until power is restored, and

The “beep” output signal from pin 6 of the microprocessor 35 is suppliedto the base of a transistor Q5 via resistor R8. A beeper B is connectedin the emitter-collector circuit of the transistor Q5 so that wheneverthe transistor Q5 is turned on by the “beep” signal, the beeper B isactivated by current flow from a low-voltage (e.g., 12 volts) powersupply 40 through the beeper B and the transistor Q5 to ground.

For the “time out” signal, the microprocessor 35 starts measuring apreselected time interval (e.g., 10 minutes) when the signal from thefloat switches 20 and 21 indicates that the liquid level in the sump hasrisen to a level high enough to close the float switches, which is whenthe pump drive motor is turned on. At the end of the preselected timeinterval, if at least one of the float switches is still closed (motoris still running), the microprocessor produces the “time out” signal onpin 8 to illuminate LED4, and an “alarm” signal on pin 7. This “alarm”signal is discussed in detail below. If the liquid level in the sumpdrops before the end of the preselected time interval, the floatswitches open, terminating the input signal to the microprocessor, andthe microprocessor then terminates the measurement of the preselectedtime interval in progress at that time.

For the “operation” signal, the microprocessor generates a signal at pin9 to turn LED3 on and off once each second. Thus, the flashing of LED3,due to being repetitively turned on and off, indicates that themicroprocessor is operational.

For the “low battery” signal, the microprocessor monitors the “batterystatus” signal from the timed battery-voltage-monitoring circuit (FETQ3) and generates the “low battery” signal at pin 10 to illuminate LED2whenever the “9V status” signal indicates that the battery voltage hasdropped below approximately 7.6 volts.

For the “AC out” signal, the microprocessor monitors the “AC status”signal from the voltage divider formed by resistors R12 and R13 andgenerates the “AC out” signal at pin 11 to activate the beeper B andilluminate LED 1 whenever the “AC status” signal indicates that the ACpower is out.

The 5-volt DC power supply Vcc is produced by an integrated circuit 45such as an LM7805 which receives its input on line 46 from either the12-volt supply or the backup 9-volt battery 40 and produces a regulated5-volt output Vcc on line 47. To smooth out any noise present in theinput to the integrated circuit 40, a capacitor C10 is connected betweenthe input line and ground, and a pair of capacitors C11 and C12 areconnected between the output line 47 and ground.

The backup battery 40 is typically a 9-volt battery that is used tomaintain the 5-volt Vcc supply whenever the AC power is out. Thismaintains the operation of the microprocessor 35, the beeper B and thevarious LED's controlled by the microprocessor output signals. In theillustrative embodiment, the battery 40 is connected to the integratedcircuit 45 via the slide switch SW1 and the contacts of a relay 50. Theswitch SW1 allows the user to disconnect the battery 40 after an ACoutage has been signaled by the beeper B and LED1, to avoid any furtherdrain no the battery. The relay 50 controls whether the integratedcircuit 45 receives power from the backup battery 40 or the 12-voltsupply derived from the standard AC power source. Normally, when ACpower is available, the coil 50 d of the relay 50 is energized becauseit is connected directly to the 12-volt supply, and the movable contact50 a of the relay 50 is in contact with the lower of two stationarycontacts 50 b and 50 c, connecting the 12-volt supply as the power inputfor the 5-volt supply. When the AC power fails and interrupts the12-volt supply, the coil 50 d of the relay 50 is de-energized, causingthe movable contact 50 a to move into contact with the upper stationarycontact 50 b, connecting the battery 40 as the power input for the5-volt supply. Thus, the 5-volt supply can continue to supply DC powerVcc to the microprocessor 35 and the various LED's until AC power isrestored or the 9-volt battery fails or is turned off by moving switchSW1.

A zener diode D6 is connected in series with the coil of the relay 50 toallow the use of a 5-volt relay. The zener diode D6 is set for 8 volts,which ensures that the 5-volt relay 50 will switch from the 12-voltsupply to the 9-volt battery when the 12-volt supply has dropped toabout 10 to 11 volts, which indicates that the AC power has beenterminated and the 12-volt supply is dropping fast.

A resistor R19 connected between pin 4 and Vcc is the pull-up for thereset circuit MCLR in the microprocessor, and in conjunction with acapacitor C8 resets the microprocessor 35 on powerup. Light-emittingdiodes LED1-LED4 are supplied with power from Vcc via respectiveresistors R14-R17. The output signals from the microprocessor 35 controlthe respective voltage drops across LED1-LED4, thereby controlling theirillumination.

The microprocessor 35 also produces an “alarm” output signal on pin 7whenever (1) the AC power fails or (2) the pump has been running for apreselected time period (e.g., 10 minutes). That is, the “alarm” signalis produced whenever LED1 or LED4 is illuminated. Either of theseconditions can result in an overflow of the sump, either because thepump is no longer operating because of a power outage (indicated by the“AC out” signal), or because a blockage has prevented the pump fromlowering the liquid level in the sump after the pump has been runningfor a period normally sufficient to lower the liquid level in the sumpto the level at which the pump would be turned off (indicated by the“timeout” signal). The “alarm” signal produced when either of theseconditions exists may be used to activate an alarm system, which may bean alarm system installed in the building in which said sump pump isinstalled or any security system capable of receiving such a signal viaa communication link.

The “alarm” signal produced at pin 7 of the microprocessor is suppliedthrough a resistor R30 to the base of a transistor Q10 to control thesupply of power to a relay 60 whose state is monitored by an alarmsystem. The coil 60 d of the relay 60 is connected in parallel with adiode D30 in the emitter-collector circuit of the transistor Q10 so thatwhenever the transistor Q10 is turned on by the “alarm” signal, the coil60 d is de-energized by current flow from the low-voltage power supplyVcc through the coil 60 d and the transistor Q10 to ground.

The relay 60 has a movable contact 60 a that is normally in contact witha first stationary contact 60 b, but is moved to a second stationarycontact 60 c when the coil 60 d is de-energized. The movable contact isconnected to the common line of an alarm system via terminal 34 a of thethree-terminal connector 34 accessible on the front panel of the controlunit (FIG. 5). The two stationary contacts 60 b and 60 c are connectedto the other two terminals 34 b and 34 c, respectively, of the connector34. Alarm systems typically can monitor either a normally closed or anormally open state, and thus the second line of the alarm system can beconnected to either the normally closed contact 60 b via terminal 34 b,or the normally open contact 60 c via terminal 34 c. In either case, thealarm system will detect a change-of-state in the relay 60 and activatethe appropriate alarm to notify the user of the alarm system that eithera power failure has occurred or the sump pump has been running too long,so that remedial action can be taken.

A standard crystal oscillator 36 is connected to pins 15 and 16 of themicroprocessor 35.

FIGS. 8-12 illustrate a dual-float-switch arrangement that can be usedwith either of the two embodiments described above. Thisdual-float-switch arrangement is mounted within a sump to detect changesin the water level within the sump. Two annular floats 50 and 51containing respective magnets 50 a and 51 a are mounted for slidingmovement on a central vertical tube 52 extending longitudinally througha cage 53. The magnets 50 a and 51 a cooperate with respective reedswitches 54 and 55 mounted inside the tube 52 to open and close theswitches in response to movement of the magnets along the tube 52.Specifically, the lower float 50 can move between a pair of retainingrings 56 and 57 affixed to the tube 52. The normal position of the float50 is its lowermost position resting on the lower retaining ring 56,which is the position of the float 50 and its magnet 50 a when the waterlevel in the sump is at a desired low level. When the water level rises,the float 50 slides upwardly along the tube 52 until the top of thefloat engages the upper retaining ring 57. As the float moves upwardly,its magnet 50 a causes the corresponding reed switch 54 to close,thereby producing a signal that can be used to turn on the sump pump.When the water level drops, the float 50 moves downwardly, causing thereed switch 54 to open and thereby produce a signal that can be used toturn off the sump pump.

The upper float 51 and its magnet 51 a and corresponding reed switch 55operate in the same manner as the lower float 50, magnet 50 a and switch54. Thus, the normal position of the float 51 is its lowermost positionresting on its lower retaining ring 58. When the water level rises, thefloat 51 slides upwardly along the rod 52 until the top of the floatengages its upper retaining ring 59. As the float 51 moves upwardly, itsmagnet 51 a causes the corresponding reed switch 55 to close, therebyproducing a signal that can be used to turn on the sump pump. When thewater level drops, the float 51 moves downwardly, causing the red switch55 to open and thereby produce a signal that can be used to turn off thesump pump.

The operation of the two float switches is redundant except for the factthat the upper float 51 and switch 55 respond to a slightly higher waterlevel than the lower float 50 and switch 54. Thus, in the event that thelower float 50 becomes obstructed, such as by the lodging of a solidobject between the upper surface of that float and its upper retainingring 57, the upper float 51 will still move upwardly and activate itsreed switch 55 to turn on the sump pump, thereby providing a backup forthe lower float switch.

The cage 53 helps to prevent solid materials in the sump water fromgaining access to the floats 50 and 51, thereby reducing the possibilityof obstructions blocking the movement of either magnet. The cage 53forms multiple elongated openings 60 that allow water to freely enterthe interior of the cage and cause the magnets to float, but therelatively narrow horizontal dimension of the openings 60 causes them toact as a filter or sieve that prevents solid materials larger than thatdimension from entering the cage and obstructing movement of the floats50 and 51.

Multiple holes 61 are formed in the bottom wall 62 of the cage 53 toallow small solids to exit the cage through its bottom wall 62 so thatthey do not accumulate inside the cage. In addition, the central portionof the bottom wall 62 is raised so that the wall slopes downwardly fromits center to its outer periphery where it joins the vertical side wall63 of the cage. This incline tends to promote the flow of small solidsout to the side wall of the cage where such solids can exit the cagethrough the multiple side-wall openings 60.

To facilitate mounting of the entire dual-float-switch assembly on thedischarge pipe that typically extends upwardly through a sump from thedischarge nozzle of the sump pump, a mounting bracket 65 is formed as anintegral part pf the upper end wall of the cage 53. The bracket 65 issecured by a nut 66 attached to the threaded upper end of the tube 52.The bracket forms a vertical flange 67 that is curved to match thecurvature of the outside surface of a typical sump discharge pipe, sothat the bracket 65 can be attached to such a pipe with a standard hoseclamp.

The dual-float-switch assembly of FIGS. 8-12 is preferably connected tothe control unit of FIGS. 1-4 or FIGS. 5-7 by a pair of electrical leads68 and 69 connected to the switches 54 and 55 via the central tube 52.The dual-float-switch assembly and the pump may be mounted in differentlocations within the sump, being coupled to each other only throughtheir respective electrical connections to the control unit mountedabove the sump. Separating the activation switches from the pump allowsinstallations where it may be beneficial for the pump to be submerged inmany feet of water before the water rises to a level where the pump isturned on to begin pumping water out of the sump.

The dual-float-switch assembly of FIGS. 8-12 may also be used with DCpump systems, which typically detect continuity at the reed switches. Apair of the dual-float switch assemblies may also be used with a pair ofpumps driven by AC and DC drive motors, with the DC pump being used as abackup for the AC pump. The AC pump system can be the same as describedabove. The DC pump can have its dual-float-switch assembly mounted at anelevation above that of the AC pump, so that if the AC pump does notturn on (e.g., because of a power failure), or if the sump takes inwater at a rate faster than the discharge rate of the AC pump, the waterlevel will continue to rise and cause the second dual-float-switchassembly to turn on the DC pump. In one embodiment of this dual-pumpsystem, the two pumps are pre-coupled so that they can be installed as asingle unit having a common discharge port so that only one connectionneed be made to the discharge line during installation.

When the present invention is applied to sump pumps used in sewage pits,it may be desirable to use one of the conventional float-switcharrangements that are commonly used with sump pumps for suchapplications. In that case, a current sensor may be used to monitor thelevel of current flowing in the power line to the drive motor of thepump, to supply the microprocessor with a signal indicating when thepump is operating. The current sensor may be hard-wired into the powerline to the pump motor, or the current can be monitored by detecting thefield surrounding the power line. The microprocessor can then use thesignal from the current sensor to determine the run time of the pumpdrive motor, and generate the desired “timeout” and “alarm” signals atpins 8 and 7, respectively, when the pump has been operatingcontinuously for a preselected time interval.

1-21. (canceled)
 22. A redundant float switch assembly for use in a sumpto supply electrical signals for controlling the energization andde-energization of a drive motor of a sump pump, comprising a pair ofspaced floats mounted for vertical movement, each of said floatscontaining at least one magnetic element, a pair of spaced switchesmounted for actuation by said magnetic elements when said floats arelocated at selected elevations, an electrical power source connected tosaid switches so that the actuation of said switches produces electricaloutput signals indicating the elevation of said floats containing saidmagnetic elements, and an apertured container surrounding said floats toallow vertical movement of said floats in said sump while restrictingthe access of obstructing particles to the path of vertical movement ofsaid floats.
 23. The redundant float switch assembly of claim 22 whichincludes a vertical tube on which said floats are mounted for slidingmovement, and said switches are mounted within said tube.
 24. Theredundant float switch assembly of claim 22 wherein said aperturedcontainer comprises a generally cylindrical cage, and said floats aregenerally disc-shaped for movement along the axis of said cage.
 25. Theredundant float switch assembly of claim 22 which includes an integralbracket on one end of said container to facilitate mounting of saidassembly on a sump discharge pipe.
 26. The redundant float switchassembly of claim 22 which includes limits for limiting the range ofmovement of each of said floats within said container.